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Title
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Thiamine-modified octamolybdate catalyzes solvent-free stereoselective olefin epoxidation with TBHP
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Type
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JournalPaper
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Keywords
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Vitamin B1 Thiamine Polyoxomolybdate Heterogeneous catalysis Epoxidation Stilbene
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Abstract
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Simple stirring of an acidic aqueous solution (pH=3) containing sodium molybdate and thiamine hydrochloride (VB1) at room temperature resulted in an octamolybdate-containing VB1 (MoB1) material as an efficient and cost-effective epoxidation catalyst using tert‑butyl hydroperoxide (TBHP) under solvent-free condition. The stereospecific stilbene oxidation (>99 %) observed in the presence of MoB1 can be originated from the steric hindrance of some groups on the thiamine molecule and π–π stacking interactions of its pyrimidine and/or thiazole rings with phenyl rings of stilbenes. Further olefins such as cyclooctene, indene, 1-octene, and styrenes are efficiently oxidized using MoB1/TBHP catalytic system. The catalyst is composed of two thiaminium dications (C12H18N4OS)2+ and one Mo8O26 4 – tetraanion based on different characterization techniques and chemical compositional analyses. Field Emission Scanning Electron Microscope (FE-SEM) images shows a sheet-like nanostructure for MoB1 comprising layers with thicknesses ranging from 50 to 500 nm. It exhibits a heterogeneous nature in catalysis evidenced by hot filtration test and ICP-OES analysis. X-ray photoelectron spectroscopy (XPS) indicates minor contributions of Mo in the oxidation states +V and +IV in addition to MoVI attributed to partial electron transfer from VB1 to Mo8O26 4 – . The scavenging experiments support the presence of radical species during catalysis, while, they do not damage the structural integrity of the MoB1 catalyst based on the recycling experiments and FT-IR spectra.
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Researchers
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Axel Klein (Not In First Six Researchers), Klaus Meerholz (Fifth Researcher), Selina Olthof (Fourth Researcher), Maryam Rostaminasab (Third Researcher), M J (Second Researcher), A R (First Researcher)
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